General Certificate of Secondary EducationHigher TierJanuary 2011

Chemistry CHY3HUnit Chemistry C3

Written Paper

Monday 17 January 2011 9.00 am to 9.45 am

For this paper you must have: a ruler the Data Sheet (enclosed).You may use a calculator.

Time allowed 45 minutes

Instructions Use black ink or black ball-point pen. Fill in the boxes at the top of this page. Answer all questions. You must answer the questions in the spaces provided. Do not write

outside the box around each page or on blank pages. Do all rough work in this book. Cross through any work you do not want

to be marked.

Information The marks for questions are shown in brackets. The maximum mark for this paper is 45. You are expected to use a calculator where appropriate. You are reminded of the need for good English and clear presentation in

your answers.

Advice In all calculations, show clearly how you work out your answer.

CHY3H

H

(Jan11CHy3H01)GK63129 6/6/6/6

Centre Number Candidate Number

Surname

Other Names

Candidate Signature

For Examiners Use

Examiners Initials

Question Mark

1

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TOTAL

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1 The table gives the solubility of sodium chloride in water at different temperatures.

Temperature in C 0 20 40 80 100

Solubility in g per 100 g of water 35.6 35.8 36.3 38.0 39.4

1 (a) A student plotted Graph A using the data in the table.

40 60 80035.0

36.0

37.0

38.0

39.0

40.0

20Temperature in C

Graph A

Solubilityof sodiumchloride ingrams per

100 g of water

100

1 (a) (i) Draw a smooth curve through all the points on Graph A. (1 mark)

1 (a) (ii) Use this graph to find the mass of sodium chloride that dissolves in 100 g of water at 60 C.

Mass = .............................. g(1 mark)

1 (a) (iii) A saturated solution of sodium chloride in 100 g of water is made at 60 C. It is then cooled to 20 C.

What mass of sodium chloride crystallises from the solution?

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1 (b) Another student plotted Graph B using the same data.

40 60 8000

20

40

60

80

100

20Temperature in C

Graph B

Solubilityof sodiumchloride ingrams per

100 g of water

100

The table shows the conclusion that each student made.

How solubility changes as temperature increases

1st student (Graph A) Very large increase

2nd student (Graph B) Very small increase

Suggest why the students came to such different conclusions even though they had used the same data to plot their graphs.

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(1 mark)____

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2 Good quality water is essential for life.

2 (a) In the United Kingdom, water is filtered and treated with chlorine to make it safe to drink.

Explain why the water is:

filtered ................................................................................................................................

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treated with chlorine. .........................................................................................................

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2 (b) Millions of people in Bangladesh drink water from wells that contain high levels of arsenic. Arsenic is poisonous.

The World Health Organisation recommends that there should be no more than 0.01 mg of arsenic per litre in drinking water.

The table gives some information about two instrumental methods of testing for arsenic.

Factor to consider Laboratory Instrumental Method Portable Instrumental Method

Cost of equipment 10 000 50

Skill level of technician Highly skilled Little training needed

Where test is done Laboratory only Anywhere

Time to prepare the instrument for the test 5 minutes 10 seconds

Sensitivity of the instrument

0.000001 mg of arsenic per litre of water

0.1 mg of arsenic per litre of water

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2 (b) (i) Use the information in the table to give two advantages and one disadvantage of using the Portable Instrumental Method compared with the Laboratory Instrumental Method.

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(3 marks)

2 (b) (ii) The information about these two instrumental methods was provided by the Professional Institute of Water Engineers (PIWE). The Institute has no connection with the companies that make these instruments.

Suggest why many people would accept the views of PIWE rather than the views of the companies that make the instruments.

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3 V2 rockets were used during the Second World War.

V2 rockets were powered by liquid oxygen and ethanol. Oxygen and ethanol react to produce carbon dioxide and water.

The energy level diagram represents the energy changes during this reaction.

A

Oxygen and ethanolEnergy

B

C

3 (a) On the energy level diagram what is represented by the letter:

A ........................................................................................................................................

B ........................................................................................................................................

C ........................................................................................................................................(3 marks)

3 (b) What type of reaction is represented by this energy level diagram?

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4 The periodic table on the Data Sheet may help you answer these questions.

4 (a) Many chemists have contributed to the development of the periodic table.

John Newlands was one of the first chemists who attempted to classify elements in a systematic way based on atomic weight. In 1866 he suggested that there was a repeating pattern of elements with similar properties every eighth element. Part of Newlands periodic table is shown below.

H Li Be B C N O

F Na Mg Al Si P S

Cl K Ca Cr Ti Mn Fe

Co, Ni Cu Zn Y In As Se

Br Rb Sr Ce, La Zr Di, Mo Ro, Ru

Many chemists in 1866 did not accept Newlands periodic table.

4 (a) (i) Give one piece of evidence which supports Newlands ideas.

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4 (a) (ii) Suggest two reasons why many chemists in 1866 did not accept Newlands ideas.

1 .........................................................................................................................................

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2 .........................................................................................................................................

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4 (b) Chlorine, bromine and iodine are Group 7 elements.

A student investigated the reactivity of these elements. The student added:

aqueous chlorine to potassium bromide and potassium iodide solutions aqueous bromine to potassium chloride and potassium iodide solutions aqueous iodine to potassium chloride and potassium bromide solutions.

The students results are shown below.

Solution Potassium chloride Potassium bromide Potassium iodide

Chlorine Solution turnedorange-brownSolution turned

brown

Bromine No reaction Solution turnedbrown

Iodine No reaction No reaction

4 (b) (i) Use these results to state and explain the trend in reactivity of these Group 7 elements.

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4 (b) (ii) Complete the equation below, which represents the reaction between chlorine and potassium bromide.

Cl2 + 2KBr .. + 2KCl(1 mark)

4 (b) (iii) In terms of electronic structure, state why chlorine, bromine and iodine are in Group 7.

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4 (c) Lithium, sodium and potassium are Group 1 elements.

Group 1 elements become more reactive down the group.

Explain why in terms of electronic structure.

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5 Read the information in the box and then answer the questions.

Seidlitz Powder is the name of a medicine.

Seidlitz Powder comes as two powders. One powder is wrapped in white paper and contains tartaric acid (C4H6O6). The other powder is wrapped in blue paper and contains potassium sodium tartrate (KNaC4H4O6) and sodium hydrogencarbonate (NaHCO3).

The contents of the blue paper are completely dissolved in water and then the contents of the white paper are added.

The equation which represents this reaction is:

C4H6O6 (aq) + 2NaHCO3 (aq) Na2C4H4O6 (aq) + 2H2O (l) + 2CO2 (g)

5 (a) Describe and give the result of a test to identify the gas produced in this reaction.

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5 (b) One of the chemicals in Seidlitz Powder is potassium sodium tartrate (KNaC4H4O6).

Suggest why it would be difficult to identify both potassium ions and sodium ions in potassium sodium tartrate using a flame test.

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(1 mark)

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5 (c) Some Seidlitz Powder was bought on the Internet. However, when tested, it was found to be only magnesium sulfate.

5 (c) (i) Describe and give the result of a chemical test to show that magnesium sulfate contains sulfate ions.

Test .....................................................................................................................................

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Result ..................................................................................................................................

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(2 marks)

5 (c) (ii) Magnesium sulfate contains magnesium ions.

Describe what you see when sodium hydroxide solution is added to a solution of magnesium sulfate.

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6 This label was on a bottle of vinegar.

Vinegar contains ethanoic acid, which is a weak acid.

6 (a) (i) According to Arrhenius, acids are chemicals that produce hydrogen ions (H+) in aqueous solution.

Complete the following equation to show why ethanoic acid (CH3COOH) is an acid in aqueous solution.

CH3COOH (l)water ................................. (aq) + ................................. (aq)

(1 mark)

6 (a) (ii) Explain the meaning of weak in terms of ionisation.

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6 (a) (iii) What is the Brnsted and Lowry definition of acids?

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6 (b) 25.0 cm3 of diluted vinegar were placed in a conical flask using a pipette.

The volume of sodium hydroxide solution needed to react completely with the ethanoic acid in 25.0 cm3 of diluted vinegar can be found by titration using phenolphthalein indicator.

6 (b) (i) Why is phenolphthalein used instead of methyl orange for this titration?

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6 (b) (ii) Describe how you would do the titration.

You should include the names of any apparatus you would use.

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6 (c) The ethanoic acid in 25.0 cm3 of diluted vinegar reacted completely with 15.0 cm3 of sodium hydroxide solution of concentration 0.10 moles per cubic decimetre.

The equation which represents this reaction is:

CH3COOH + NaOH CH3COONa + H2O

Calculate the concentration of ethanoic acid in moles per cubic decimetre.

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Concentration = .................................................. moles per cubic decimetre(2 marks)

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7 Hydrogen peroxide is often used to bleach or lighten hair.

Hydrogen peroxide slowly decomposes to produce water and oxygen.

7 (a) The equation for the reaction can be represented using structural formulae.

2 H O O H 2 H O H + O = O

Use the bond energies in the table to help you to calculate the energy change for this reaction.

Bond Bond energy in kJ per mole

H O 464

O O 146

O = O 498

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Energy change = ........................................ kJ(3 marks)

7 (b) Explain, in terms of bond making and bond breaking, why the reaction is exothermic.

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END OF QUESTIONS

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